What is spray drift? Why does it matter?

Spray drift is the movement of small airborne drops containing pesticide that are blown by wind from the area you are treating [the treatment zone/area] to another area usually downwind.

Spray drift is to be avoided because although the actual volumes of spray drift may be low, their presence or activity on sensitive plant/animal species, may cause harm. In addition:

• drift deposits may build up in one area to form a higher concentration of pesticide;
• drifting drops that land on non-sprayed vegetation may pollute and damage that vegetation. There are many reports of adjacent crops being damaged by drifting herbicide sprays and in some cases crops are reported as being contaminated or ‘tainted’ by pesticides and rendered unusable for food.
• Drifting drops may also pollute water in rivers and wells or deposit upon bystanders and buildings.

All pesticide users must take full care to avoid drift when spraying. If wind speeds are too high then operators must accept that they will either not have to spray at all or delay the application until weather conditions are better and it is safe to spray.

Many government led initiatives now evaluate and rank drift reducing nozzles and sprayers. The most effective of these may be used to spray closer to environmentally sensitive zones than could otherwise be done with conventional nozzles/sprayers. The section on nozzle selection and their optimised use may be useful. 

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